Lawmakers should put today's technology to use and pursue a statewide early alert system.

The San Andreas Fault is overdue for a powerful earthquake, geologists say, but there is no way to predict when it will strike. Yet as Japan has demonstrated, it is possible to detect the start of a quake and alert at least some potential victims moments before the most damaging shocks hit. That country's detection and warning system helped minimize the casualties from the massive quake off its coast in 2011, although the resulting tsunami claimed thousands of lives.

Last week, scientists at the U.S. Geological Survey, the California Institute of Technology and UC Berkeley, backed by state Sen. Alex Padilla (D-Pacoima), called on the state to develop a similar system. They want to upgrade the existing California Integrated Seismic Network, a joint effort by federal, state and university geologists to monitor seismic activity along multiple fault lines, to deliver alerts to the public when a sizable quake strikes. It's an idea worth pursuing, although policymakers shouldn't minimize the challenges that remain.

Earthquakes in California typically start about 5 miles below the surface when giant land masses shift. The first sign of trouble is a wave of compression that ripples outward, followed by more vigorous (and potentially damaging) shaking. The gap between the compression (known as P waves) and the slower-moving vibrations that follow (called S waves) is what creates an opportunity for a quake alert system. Theoretically, seismometers could gather data about the P waves, then computers could calculate the intensity of the quake and send an alert before the S waves have reached much of the population.

The nontrivial challenge, however, is analyzing the data from the P waves quickly enough to provide a timely warning, yet without sending out false alarms. Lots of events other than earthquakes can rattle the ground enough to be detected by a seismometer. And it may not be clear from the initial burst of underground energy just how bad a quake will be.

Scientists working on the state's seismic network have developed a trial version of an early warning system that can trigger an alert within about 8 seconds of an underground rupture. Such a delay would give a quake's S waves enough time to travel about 18 miles from the epicenter before the alert sounded. If the technology had been in place during the 1994 Northridge earthquake, the temblor would have passed through downtown Los Angeles before the first warning went out.

With a blind zone that large, taxpayers might question whether it's worth investing in an alert system at all. Seismologists working on the project insist that they can speed the analysis significantly and cut the size of the blind zone as they perfect the system. But developing faster and more reliable detection technology will require more software engineers and more seismometers because even the most effective algorithms can't prevent a blind zone if there's no seismometer within miles of the epicenter. They estimate that for $16 million a year — about twice what the federal and state governments now spend on the seismic system in California — they can develop and operate an alert system they can start phasing into service within two years.

The state's effort has at least one potential ally — or rival — in the private sector. Seismic Warning Systems of Scotts Valley, which aims to build its own statewide network of quake sensors, says its patented technology can verify the start of an earthquake and send out an alert in less than 1 second. In a decade of providing alerts to industrial sites, fire stations and schools, executives claim, their technology has yet to register a false alarm. Officials at the state seismic network are skeptical but say they can't verify or debunk the company's claims because it won't share its data.

The biggest drawback to Seismic Warning System's approach is that the company is unwilling to send alerts to the general public. Its executives argue that doing so could cause more harm than good; not knowing what to do in an earthquake, many people would unwittingly put themselves in harm's way. And if there were false alarms, the public might come to disregard legitimate alerts. But that's a reason to educate the public, as Japan has done, not to withhold potentially life-saving information from it.

Nevertheless, the efforts of companies such as Seismic Warning Systems could be an important supplement to the state's seismic alerts. Even with the investment proposed by Padilla, private industry will still need to translate an alert from the state network into the right preventive response, such as automatically stopping trains, closing pipeline valves and opening garage doors (to prevent them from being jammed shut). And some industrial sites and corporate customers may seek even more advance notice than the state network can deliver.